High efficiency photoelectrochemical (PEC) systems to produce hydrogen directly from water using sunlight as the energy source have been identified as a promising technology to meet long-term hydrogen-production goals at the United States Department of Energy.
Photoactive devices with separate cathodes and anodes have been used in the art. Cathodes may include triple-junction amorphous silicon alloy (a-Si) type solar cell on a tin-oxide coated glass superstrate and may be physically separated from the anodes but electrically connected, e.g. using external wires.
Additionally, fully integrated photoelectrode designs without external wires have included triple-junction a-Si cells on a stainless steel substrate, some where the back surface of the substrate was coated with cobalt-molybdenum (CoMo) hydrogen evolution reaction (HER) catalyst while the front surface of the device was coated with Fe:NiOx an oxygen evolution reaction (OER) catalyst. Such devices are prone to having high optical losses, loss of catalytic activity, and reduced corrosion protection at the OER catalyst layer.
There is a need for alternative PEC device configurations with increased solar conversion efficiencies and enhanced long-term stability which allow production of one or more desired gases from materials containing constituents of those gases, e.g. liquids such as aqueous electrolytes, without the need for any external electrical biasing.